Mr. Sims, former director of strategic communications for the president, is out with a new book, “Team of Vipers,” which gives an often-unflattering portrayal of a chaotic work environment at the White House.

The president on Tuesday said of the book:

“A low level staffer that I hardly knew named Cliff Sims wrote yet another boring book based on made up stories and fiction. He pretended to be an insider when in fact he was nothing more than a gofer. He signed a non-disclosure agreement. He is a mess!”

The White House has said Mr. Sims was not part of the president’s inner circle.

In his book, Mr. Sims describes helping the president to compile a list of leakers inside the White House. He also characterizes White House counselor Kellyanne Conway as a chronic leaker who nevertheless enjoys the president’s confidence because she defends him fiercely on TV.

Ms. Conway responded to his accusation, “The real leakers, past and present, get much more positive press than I do. While it’s rare, I prefer to knife people from the front, so they see it coming.”